1. Field of the Invention
The invention relates to semiconductor processing, particularly to techniques for growing silicon crystal.
2. Description of the Background Art
Single-crystal silicon is used commonly as the starting material for fabricating integrated circuits. A typical technique for producing single-crystal silicon is the so-called Czochralski process, whereby a small single-crystal seed is dipped into molten silicon and slowly withdrawn, typically while simultaneously rotating the crystal. In this way, the single crystal is grown into a larger silicon crystal or boule.
To produce high-quality silicon crystals, certain conditions that affect crystal growth are carefully controlled, such as temperature, pressure, impurities, and pull rate. In addition, certain impurities may be intentionally introduced into the molten silicon, as "dopants," to alter the electrical characteristic of the resulting crystal. But sometimes, impurities unintentionally contaminate the molten silicon such that crystal growth is disrupted, typically by the impurities precipitating at interstitial or vacant sites, thereby stressing the crystal lattice.
Accordingly, there is a need to improve conventional Czochralski processing by reducing disruption of crystal growth caused by impurities.